1. Field of the Invention
The invention relates to a microcapsule reagent suitable for immunological response, more particularly to a microcapsule reagent suitable for an antigen-antibody response which provides high sensitivity, is stable and causes non-specific agglutination only with difficulty.
2. Development of the Invention
In order to facilitate an antigen-antibody response of high sensitivity in a simple manner, an immunological agglutination method in which an antigen or antibody is carried on a water-insoluble carrier which causes agglutination based on an antigen-antibody response which can be seen with the naked eye has been employed.
Red blood cells of animals such as chicken, alligators, sheep, etc. have been used as carriers for the antigens or antibodies, and, utilizing these carriers, passive haemagglutination (PHA) has generally been used since this method provides high sensitivity with simple operations. Recently, a method has been used for semi-qualitatively determining the presence or absence of antigens or antibodies very efficiently in a simple manner which is called the microtiter system. However, the microtiter system involves disadvantages, e.g., due to the use of animal-originated carriers, red cell carriers per se are antigenetic and cause specific agglutination to adversely affect the desired antigen-antibody response; further, efficiency is not uniform based on differences between subjects, changes with the passage of time, and cost is high.
A latex agglutination method in which a polystyrene latex is used as a carrier has also been put into practical use. While the disadvantages encountered with the use of animal-originated carriers is eliminated by this method, this method also involves disadvantages, e.g., not only is sensitivity poor as compared to the passive haemagglutination method, but storability over long periods of time is poor because of a weak bond with an antigen or antibody. Further natural agglutination--which is not based on an antigen-antibody response--tends to occur, etc.
In U.S. Ser. No. 110,318 filed Jan. 8, 1980, a method for detecting an antibody or antigen using microcapsules having an antigen or antibody bound to the wall surface thereof via antigen-antibody agglutination is proposed. Further, in order to improve the detection sensitivity of such microcapsules, microcapsule reagents in which specific wall materials such as polyurea, polyurethane, etc., are employed are also proposed. By the use of such microcapsule reagents, improved detection sensitivity is attained, but such systems are not satisfactory from the standpoint of storability over long periods of time.